Multilayer materials

ABSTRACT

The invention is directed to a composite material, especially a biomedical device, e.g. an ophthalmic device, preferably a contact lens, with one or more wettable surfaces capable of holding a continous layer of aqueous fluid thereon which composite material comprises a bulk material and a hydrophilic coating characterized in that the hydrophilic coating consists of a carbohydrate attached covalently to reactive groups at the surface of the bulk material, either directly or via functional groups of an oligofunctional compound, said oligofunctional compound in turn having functional groups being capable of reacting with said reactive groups at the surface of the bulk material and with the carbohydrate, wherein said reactive groups are either inherently (a priori) present in the bulk material or wherein said reactive groups have been attached to the surface of the bulk material by a plasma surface preparation, as well as to a process of manufacture of such a composite material.

This application is a continuation of application Ser. No. 08/240,738filed on May 12, 1994 now abandoned which is a 371 of PCT/EP93/02420,filed Sep. 8, 1993.

This invention relates to composite materials for biomedical use thatpossess considerably improved retention of an aqueous layer on thesurfaces. The invention also relates to the production of such materialsfrom materials that possess suitable bulk properties, but inadequateretention of an aqueous layer. In a particular aspect, the materials andmethod of this invention are useful for the fabrication of ophthalmicdevices, e.g. contact lenses.

BACKGROUND TO INVENTION

There are many applications of materials where retention of a thin filmof aqueous fluid is desirable. For example, the retention of an aqueousfluid layer is beneficial for lubrication of catheters, the retention ofan aqueous fluid layer can reduce protein fouling on the surface ofpacemakers and artificial vascular grafts, or the retention of anaqueous fluid layer can prevent the colonization of a surface bybacteria as they are unable to attach properly. In another aspect, thefacile movement of an eyelid over a contact lens is important for thecomfort of the wearer; this sliding motion is facilitated by thepresence of a continuous layer of tear fluid on the contact lens, alayer which lubricates the tissue/lens interface. However, clinicaltests have shown that currently available contact lenses partially dryout between blinks, thus increasing friction between the eyelid and thelens. The increased friction results in soreness of the eyes andmovement of the contact lens. Since the average period between blinks isca. 12 seconds, it would be advantageous to fabricate a wettable andbiocompatible contact lens that can hold a continuous layer of tearfluid for more than 12 seconds. Current biomedical materials do notreach this target; for instance, contact lenses fabricated from highlywater swellable polymer pHEMA retain such a tear layer for approximately5 seconds only.

Thus materials with wettable and biocompatible surfaces are highlydesirable for many applications. The wettability of materials isstrongly dependent on the chemical composition of the material surface.In particular, the ability of the surface to hold a continuous layer ofan aqueous solution, such as tear fluid, is affected by the compositionof the material surface. Early attempts to solve the wettability problemin the ophthalmic field were based on producing hydrophilic materials.For example, in an attempt to make wettable soft contact lenses,silicone elastomers with pendant epoxy groups were prepared bycrosslinking epoxidized silicone compounds (French patent FR 2,622,201,J. M. Frances and G. Wajs). The elastomers were rendered wettable bygrafting glucuronic acid onto the epoxy groups. The disadvantage ofincorporating hydrophilic species into polymers by bulk synthesis isthat the optimum balance of optical properties (e.g., transparency andrefractive index), mechanical properties (e.g. strength, hardness, gaspermeability and elasticity) and processability of the materialobtainable will be worse than conventional materials and may not satisfythe application. The incorporation of hydrophilic monomers is notappropriate for improving the wettability of fluoropolymer- oracrylate-based lenses.

In an attempt to fabricate hard contact lenses which are compatible withthe cornea and ocular fluid, dextran ester monovinyl compounds have beencopolymerised with various acrylates (Japanese patent JP 63/309914, H.Kitaguni et al.). Dextran/methyl methacrylate copolymers have beenprepared by graft polymerisation and have yielded wettable contactlenses (Y. Onishi et al. in Contemp. Top. Polym. Sci. 4, 149 (1984)).The preparation of dextran ester copolymers by bulk polymerisationmethods offers limited scope for improving the wettability of contactlenses in general. The disadvantage of incorporating hydrophiliccompounds into polymers by bulk synthesis is that the optical properties(e.g., transparency and refractive index), mechanical properties (e.g.,strength, hardness, gas permeability and elasticity) and processabilityof the material cannot be optimized independently.

A method of modifying the surface of contact lenses has been disclosedin GB 2,163,436 Halpern). According to said method the lens is coatedwith a carbohydrate which is then crosslinked either covalently with apolyisocyanate or electrostatically with a divalent cation. The processresults in a crosslinked skin which is not covalently bonded to the lensand will delaminate when subjected to a shearing force e.g. by aneyelid.

An alternative approach has been disclosed in WO 90/04609 (Sepracor).Polymeric substrates, especially polymeric membranes, having reactivegroups such as hydroxy or amino groups at the ends of the polymer chainsthereof are reacted with a polyfunctional linker moiety having terminalgroups such as epoxy, carbonyl, carboxy, amino, halo, hydroxy,sulfonylhalide, acyl halide, isocyanato, or combinations thereof, whichin turn are bonded with a ligand such as hydroxyethylcellulose ordextran. Since the molecular weight of the polymer chains in thesubstrate is high, the density of chain ends, especially at the surface,will be low, and therefore the density of grafted polysaccharide chainswill be low.

The use of dextran and other carbohydrates for surface modification ofpolymers has also been reported by WO 83/03977, however, in that casethe linker moiety is a silane and articles to be treated such as contactlenses are not disclosed.

Additional prior art is directed to modification of the surfaces ofcontact lenses (U.S. Pat. No. 5,080,924) or ocular implants (WO93/03776), respectively, wherein amino groups at the surface thereof arereacted with dialdehydes and are then coupled with polysaccharides.However, the reaction of an aldehyde with the hydroxyl groups of apolysaccharide will yield an acid-labile ketal bond.

The above methods all require the presence of the article of achemically reactive group suitable for the intended covalent reaction.Many materials of interest for ophthalmic applications and implantablebiomaterial devices do not possess suitable reactive surface groups, forinstance, silicon-based contact lenses and polytetrafluoroethylenevascular grafts. The present invention also comprises methods for theactivation of a device surface, the method being generic, so that thesurface of any material with suitable bulk properties can be convertedto be receptive for the covalent immobilization of a coating which ishighly retentious for aqueous layers. In this embodiment of theinvention the surface of the polmyeric material is activated preferablyby a gas plasma (glow discharge) surface treatment method.

A number of surface treatment techniques for polymeric materials areknown in the art: Corona Discharge, Flame Treatment, Acid Etching, and anumber of other methods intended to perform chemical modification of thesurface. Among the disadvantages of these techniques are the use of orproduction of hazardous chemicals, the often excessive depth oftreatment, non-uniformity of treatment at a microscopic level, and oftensevere etching and pitting that leads to changes in surface topography.The depth of treatment is important because with clear materials such asthose required for lenses the optical clarity and surface smoothnessbecome affected after an excessively harsh treatment.

Treatment of polymeric surfaces by gas plasmas provides the advantagesof very low treatment depth, and uniformity on a microscopic scale. Agas plasma (also known as glow discharge) is produced by electricaldischarge in a gas atmosphere at reduced pressure (“vacuum”). It createsa stable, partially ionized gas that may be utilized for effectingreactions on the surface of the substrate because the gas plasmaenvironment activates even chemical compounds that are unreactive undernormal conditions. The treatment intensity at the surface is generallyrelatively strong, and yet the penetration depth of gas plasma treatmentis very low, of the order of 5 to 50 nanometres, at a treatmentintensity sufficient for useful surface modification. Surface topographyand optical clarity do not change unless exposure to the plasma isperformed for periods of time much exceeding the time required forachieving the desired chemical modification of the surface. Thereoccurs, therefore, significantly less alteration of the properties ofthe bulk material than with alternative treatment technologies.

Gas plasma techniques can have two classes of outcomes. In the first,commonly called plasma surface treatment, the surface of a polymericmaterial to be treated (“the substrate”) is subjected to a plasmaestablished in one or more inorganic vapors or some select organicvapors, and the plasma treatment causes the replacement of some of theoriginal chemical groups on a polymer surface by other, novel groupswhich are contributed from the plasma gas. For instance, the plasmasurface treatment of polytetrafluoroethylene in an ammonia plasma leadsto the abstraction of some of the surface fluorine atoms by C—F bondbreakage and the incorporation into the modified surface layer of aminegroups by C—N bond formation. Plasma surface treatment in an appropriatevapor such as ammonia, carbon dioxide, or water vapor, can therefore beused to place on the surface of any polymeric material reactive chemicalgroups, such as amine, carboxyl, or hydroxyl, suitable for thesubsequent covalent immobilization of various molecules.

The second type of plasma technique is commonly called plasmapolymerization and occurs when a discharge is struck in most organicvapors. In contrast to plasma surface treatment, in which less than amonolayer of new material is added, the technique of plasmapolymerization leads to the formation of film coatings which can beseveral micrometers thick and can completely mask the substrate.

Plasma polymers are also covalently bonded to the underlying substrate.The covalent attachment of the plasma coating to the bulk materialensures that the plasma polymer does not detach. Furthermore, plasmapolymers are highly crosslinked and do not possess low molecular weightfragments which might migrate into body tissue or fluids.

By appropriate choice of the monomer vapor and the plasma conditions,plasma polymer coatings can be fabricated to contain specific,chemically reactive groups which are also suitable for the subsequentchemical attachment of various molecules to the surface. In the presentinvention, the surface of a polymeric material which does not inherentlycarry suitable reactive groups can be activated by plasma surfacetreatment, plasma polymerization, or plasma polymerization followed by asubsequent plasma surface treatment.

SUMMARY OF INVENTION

Accordingly, in one aspect, the invention provides a novel compositematerial, especially a biomedical device, e.g. an ophthalmic device,such as a contact lens, with one or more wettable surfaces capable ofholding a continuous layer of aqueous fluid thereon, characterized inthat the composite comprises a carbohydrate which is covalently bound bya hydrolytically stable bond to a plasma surface prepared on the basematerial. Within the context of this invention a plasma surface preparedon a base, or bulk, material comprises either a plasma treated (ormodified) surface on a base material or a plasma polymer coated to abase material. The base material is selected for it's bulk properties,such as mechanical strength, elasticity, gas permeability, opticalclarity, to suit the intended application of the composite.

In a second aspect, the invention provides a biomedical product whichprovides enhanced comfort to the wearer, whereby said product iscomposed of a bulk material and a hydrophilic coating according to thefirst aspect of the invention. The hydrophilic coating consists of acarbohydrate attached covalently on to a plasma surface prepared on thebulk material, e.g. a thin, fully covering plasma polymer coating.

In a further aspect the invention provides a composite material,especially a biomedical device, e.g. an ophthalmic device, such as acontact lens, with one or more wettable surfaces capable of holding acontinuous layer of aqueous fluid thereon characterized in that thecomposite comprises a carbohydrate which is covalently bound by ahydrolytically stable bond to reactive groups inherently present in thebulk material and at the surface of the biomedical device.

According to these aspects of the invention the carbohydrate is bound tothe reactive groups either directly or via an oligofunctional compoundhaving one or more functional groups capable of chemically reacting withthe said reactive groups and having at least one additional functionalgroup capable of chemically reacting with a carbohydrate to produce anactivated surface.

In yet a further aspect, the invention provides a process for themanufacture of a wettable composite material, especially a biomedicaldevice, e.g. an ophthalmic device, said process comprising the followingsteps:

1. exposing the non-composite biomedical device in its desired finalform to a low pressure plasma in a vapor of at least one organic and/orinorganic compound under conditions whereby a thin film containingreactive groups is deposited on the desired surface(s) of the basematerial,

2. optionally, reacting the said reactive groups with an activatinggroup, and/or with an oligofunctional compound having one or morefunctional groups capable of chemically reacting with the said reactivegroups, or with the activated reactive groups, and having at least oneadditional functional group capable of chemically reacting with acarbohydrate to produce an activated surface,

3. optionally treating the carbohydrate with a reagent which modifiesthe said carbohydrate so that it is capable of reacting with the surfacereactive or functional groups,

4. reacting the reactive groups or the functional groups with thecarbohydrate,

5. optionally, treating the surface-immobilized carbohydrate with areagent to stabilize the bond between the carbohydrate and the surface.

The resulting material is preferably washed and suitably packed readyfor use.

In yet a further aspect, the invention provides a process for themanufacture of a wettable composite material, especially a biomedicaldevice, e.g. an ophthalmic device, having reactive groups inherently (apriori) present in the bulk material, said process comprising thefollowing step(s):

optionally, reacting the reactive groups inherently present in the bulkmaterial of the non-composite biomedical device in its desired finalform with an activating group, and/or with an oligofunctional compoundhaving one or more functional groups capable of chemically reacting withthe said reactive groups, or with the activated reactive groups, andhaving at least one functional group capable of chemically reacting witha carbohydrate to produce an activated surface,

optionally treating the carbohydrate with a reagent which modifies thesaid carbohydrate so that it is capable of reacting with the surfacereactive or functional groups,

reacting the reactive groups or the functional groups with thecarbohydrate,

optionally, treating the surface-immobilized carbohydrate with a reagentto stabilize the bond between the carbohydrate and the surface.

The invention is therefore directed to a composite material, especiallya biomedical device, e.g. an ophthalmic device, preferably a contactlens, with one or more wettable surfaces capable of holding a continuouslayer of aqueous fluid thereon which composite material comprises a bulkmaterial and a hydrophllic coating characterized in that the hydrophiliccoating consists of a carbohydrate attached covalently to reactivegroups at the surface of the bulk material, either directly or viafunctional groups of an oligofunctional compound, said oligofunctionalcompound in turn having functional groups being capable of reacting withsaid reactive groups at the surface of the bulk material and with thecarbohydrate, wherein said reactive groups are either inherently (apriori) present in the bulk material or wherein said reactive groupshave been attached to the surface of the bulk material by a plasmasurface preparation, as hereinbefore defined, as well as to a process ofmanufacture of such a composite material.

The bulk material may be e.g. any material conventionally used for themanufacture of biomedical devices, e.g. contact lenses, which are nothydrophilic per se. Such materials are known to the skilled artisan andmay comprise for example polysiloxanes, fluorinated (meth)acrylates orequivalent fluorinated comonomers derived e.g. from other polymerizablecarboxylic acids, alkyl (meth)acrylates or equivalent alkyl comonomersderived from other polymerizable carboxylic acids, or fluorinatedpolyolefines, such as fluorinated ethylene propylene, ortetrafluoroethylene, preferably in combination with specific dioxols,such as perfluoro-2,2-diethyl-1,3-dioxol. Examples of suitable bulkmaterials are e.g. Neofocon, Pasifocon, Telefocon, Silafocon,Fluorsilfocon, Paflufocon, Silafocon, Elastofilcon, Fluorofocon orTeflon AF materials, such as Teflon AF 1600 or Teflon AF 2400 which arecopolymers of about 63 to 73 mol % of perfluoro-2,2-diethyl-1,3-dioxoland about 37 to 27 mol % of tetrafluoroethylene, or of about 80 to 90mol % of perfluoro-2,2-dimethyl-1,3-dioxol and about 20 to 10 mol % oftetrafluoroethylene.

The bulk material may also be e.g. any material conventionally used forthe manufacture of biomedical devices, e.g. contact lenses, which arehydrophilic per se, since reactive groups, e.g. amine or hydroxy groupsare inherently present in the bulk material and therefore also at thesurface of a biomedical device manufactured therefrom. Such materialsare known to the skilled artisan. Typical examples comprise e.g.Polymacon, Tefilcon, Methafilcon, Deltafilcon, Bufilcon, Phemfilcon,Ocufilcon, Focofilcon, Etafilcon, Hefilcon, Vifilcon, Tetrafilcon,Perfilcon, Droxifilcon, Dimefilcon, Isofilcon, Mafilcon or Atlafilcon.Most of these materials are HEMA based, but suitable materials may alsobe based on other underlying monomers or polymers having reactivegroups, e.g. hydroxy groups or amino groups, such as e.g. polyvinylalcohol.

The bulk material may be any blood-contacting material conventionallyused for the manufacture of renal dialysis membranes, blood storagebags, pacemaker leads or vascular grafts. For example, the bulk materialmay be a polyurethane, polydimethylsiloxane, polytetrafluoroethylene,polyvinylchloride or Dacron™.

Moreover, the bulk material may also be an inorganic or metallic basematerial with or without suitable reactive groups, e.g. ceramic, quartz,or metals, such as gold, or other polymeric or non-polymeric substrates.E.g. for implantable biomedical applications, ceramics, preferablycoated with a polysaccharide, are very useful. In addition, e.g. forbiosensor purposes, dextran coated base materials are expected to reducenonspecific binding effects if the structure of the coating is wellcontrolled. Biosensors may require polysaccharides on gold, quartz, orother non-polymeric substrates.

The reactive groups, inherently (a priori) present at the surface of thebulk material or having been introduced or attached to the surface ofthe bulk material by a plasma surface preparation, as hereinbeforedefined, may be selected from a wide variety of groups well known to theskilled artisan. Typical examples are e.g. hydroxy groups, amino groups,carboxy groups, carbonyl groups, aldehyde groups, sulfonic acid groups,sulfonyl chloride groups, groups being replaceable by amino or hydroxygroups, such as halo groups, or mixtures thereof Amino groups andhydroxy groups are preferd.

Suitable organic or inorganic compounds for the plasma surfacepreparation step are e.g. ammonia, water vapor, carbon dioxide, carbonmonoxide, noble gases, e.g. argon, oxygen, ozone or air, alcohols,amines or alkanones, preferably lower alkanols having up to eight carbonatoms, lower alkyl amines having up to eight carbon atoms, or loweralkanones having up to eight carbon atoms, e.g. methanol, ethanol,ammonia, methylamine, ethylamine, heptylamine, or acetone, or many othercompounds known to those skilled in the art of plasma surfacepreparation. It is also within the scope of this invention to usemixtures of the compounds mentioned hereinbefore.

The first step of deposition of plasma polymer thin film coatingscontaining on their surfaces reactive groups such as amine and hydroxylgroups is fully described in the applicants International PatentApplication PCT/AU89/00220 (Griesser et al.) and in Griesser H. J. andChatelier R. C. Journal of Applied Polymer Science: Applied PolymerSymposium 46, 361-384 (1990);

Suitable activating compounds for the optional step 2 are e.g.anhydrides or activated esters, such as 2,2,2-trifluoroethanesulphonylchloride, p-toluenesulphonyl chloride, cyanogen bromide orp-nitrophenylesters.

Suitable oligofunctional compounds for the optional step 2 havepreferably up to four functional groups and are, more preferred,bifunctional. Preferred bifunctional compounds for step 2 are preferablyepihalohydrins, bis-oxiranes or diisocyanates. Typical examples are e.g.the diglycidyl ether of bisphenol A, 1,3-butadiene diepoxide or thediglycidyl ether of 1,4-butanediol. These bifunctional compounds yieldan activated surface with pendant epoxy groups, halogen groups orisocyanato groups. However, the present invention is not limited to theuse of epoxy, halogen or isocyanato groups as functional groups. Manyother oligo- or bifunctional reactive compounds can effect the desiredcovalent crosslinking between a reactive group rich coating, e.g. ahydroxyl or amine rich coating, and a carbohydrate. For example, othersuitable bifunctional compounds are diacid chlorides, ditosylates,dihydrazides and any compound which contains more than one functionalgroup which can react with the reactive groups as hereinbefore defined.A preferred embodiment of the invention is the use of epihalohydrins,bis-oxiranes (diglycidyl ethers) or diisocyanates as oligofunctionalcompounds. It is further preferred that said oligofunctional compounds,or in the preferred case the bifunctional compounds, have differentreactivity with respect to their functional groups, or to their twofunctional groups, respectively.

Suitable epihalohydrins are e.g. epichlorohydrine ormethylepichlorohydrin.

One class of bis-oxirane compounds comprises diglycidyl compounds offormula I

wherein D is an organic divalent radical and wherein each of theglycidyloyxy groups are covalently bonded to a carbon atom of D.Preferably the compounds of formula I are polyglycidyl ethers orcarboxylate esters.

The organic radical D may be aliphatic, heterocyclic, aromatic, oraraliphatic which is bound to the glycidyl oxygen directly or through acarbonyl group.

In one preferred embodiment D is aliphatic. Especially suitable radicalsinclude alkylene of up to 25 carbon atoms, or said alkylene interruptedby one or more hetero atoms, such as oxygen, or cyclohexylene. Morepreferably, D is alkylene of 2 to 6 carbon atoms, or—C₂-C₄-alkylene(O—C₂-C₄-alkylene)_(p) where p is 1 to 8. Also especiallysuitable are the aforementioned aliphatic radicals terminating incarbonyl groups to form the corresponding diglycidyl carboxylate ester.

In another preferred embodiment D is aromatic. Especially suitablearomatic radicals include phenyl, biphenyl, phenyl-loweralkylene-phenyl, phenyloxyphenyl, or phenylsulfonylphenyl, which arefurther unsubstituted or are substituted by lower alkyl, lower alkoxy,or halo.

The term “lower”, whenever used in the context of this invention and ifnot defined otherwise, defines groups having up to seven carbon atoms,preferably groups having up to four carbon atoms. Thus, for the reasonof illustration, e.g. lower alkyl is alkyl having up to 7 carbon atom,such as methyl, ethyl, propyl, butyl, or hexyl, and lower alkoxy isalkoxy having up to 7 carbon atoms, such as methoxy, ethoxy, butoxy, orheptyloxy.

Another class of bis-oxirane compounds comprises polyglycidyl compoundsof the formula II

wherein E is an organic divalent radical and wherein each of theglycidyl radicals are covalently bonded to a nitrogen or carbon atom ofE. Preferably E is aliphatic, aromatic, heterocyclic or araliphatic, ashereinbefore defined for radical D.

In a preferred subembodiment E is a bivalent hydantoin radical which isbound to the glycidyl groups through the respective nuclear nitrogenatoms, and said hydantoin is otherwise unsubstituted or substituted bylower alkyl.

In an alternate preferred subembodiment E is alkylene of up to 6 carbonatoms.

A third class of bis-oxirane compounds are those of the formula III

wherein m is 0, 1 or 2 and each R independently represents hydrogen orlower alkyl.

Also mixtures of the above bis-oxiranes of formulae I, II and III may beemployed. Suitable bis-oxiranes, most of which are readily available andall of which are known, and which can be used according to thisinvention, have been disclosed e.g. in U.S. Pat. No. 4,598,122.

Suitable bis-oxiranes are e.g. the diglycidyl ether of bisphenol A,1,3-butadiene diepoxide or the diglycidyl ether of 1,4-butanediol,divinylbenzene dioxide, diglycidyl ether, limonene dioxide,vinylcyclohexene dioxide, the diglycidyl ether of bisphenol F,3,4-epoxycyclohexylmethyl 3,4-epoxy-cyclohexane carboxylate, phthalicacid diglycidyl ester, diglycidyl aniline, or oligoethyleneoxidediclycidylethers, such as di(ethyleneglycol) diglydicyl ether,tetra(ethyleneglycol) diglycidyl ether, or octa(ethyleneglycol)diglycidyl ether.

Suitable diisocyanates are generally aromatic, aliphatic orcycloaliphatic diisocyanates, or mixtures thereof. The aromatic moietythereof is preferably phenyl, naphthyl or anthryl, which areunsubstituted or substituted by alkyl having up to four carbon atoms, byalkoxy having up to four carbon atoms or by halo, preferably chloro,wherein two aromatic moieties may be connected by an ether bond or by analkenylene group of up to four carbon atoms, the aliphatic moietythereof is preferably alkyl having up to 10 carbon atoms, thecycloaliphatic moiety thereof is preferably cycloalkyl or bicycloalkylhaving up to 6 carbon atoms in each cycloalkyl ring.

Examples of such diisocyanates are toluene-2,4-diisocyanate,toluene-2,6-diisocyanate, isophorone diisocyanate, ethylenediisocyanate, ethylidene diisocyanate, propylene-1,2-diisocyanate,cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate,m-phenylene-1,2-diisocyanate, 3,3′-diphenyl-4,4′-biphenylenediisocyanate, 4,4′-biphenylene diisocyanate, 4,4′-diphenylmethanediisocyanate, 3,3′-dichloro-4,4′-biphenylene diisocyanate, 4,4′-diphenyldiisocyanate, 1,6-hexamethylene diisocyanate,2,2,4-trimethyl-hexamethylene diisocyanate, 1,4-tetramethylenediisocyanate, 1,10-decamethylene diisocyanate, cumene-2,4-diisocyanate,1,5-naphthalene diisocyanate, methylene dicyclohexyl diisocyanate,1,4-cyclohexylene diisocyanate, p-tetramethyl xylylene diisocyanate,p-phenylene-1,4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate,4-chloro-1,3-phenylene diisocyanate, 4-bromo-1,3-phenylene diisocyanate,4-ethoxy-1,3-phenylene diisocyanate, 2,4-dimethyl-1,3-phenylenediisocyanate, 5,6-dimethyl-1,3-phenylene diisocyanate,2,4-diisocyanatodiphenylether, 4,4′-diisocyanatodiphenylether, benzidinediisocyanate, 4,6-dimethyl-1,3-phenylene diisocyanate, 9,10-anthracenediisocyanate, 4,4′-diisocyanatodibenzyl,3,3′-dimethyl-4,4′-diisocyanatodiphenylmethane,2,6dimethyl-4,4′-diisocyanatodiphenyl, 2,4-diisocyanatostilbene,3,3′-dimethoxy-4,4′-diisocyanatodiphenyl, 1,4-anthracene diisocyanate,1,8-naphthalene diisocyanate, 1,3-bis-isocyanatomethyl-cyclohexane, or4,4′-(dicyclohexyl)methane diisocyanate.

Preferred are diisocyanates having different reactivity with respect totheir two NCO groups, such as isophorone diisocyanate, 2,4-toluenediisocyanate, or 2,2,4-trimethylhexamethylene diisocyanate.

Suitable carbohydrates according to this invention comprise naturalproducts, modified carbohydrates and synthetic carbohydrates. Examplesfor these groups of carbohydrates are sugars, such as monosaccharides,di- and oligosaccharides, cyclic oligosaccharides, linearpolysaccharides, whether homopolysaccharides or heteropolysaccharides,branched polysaccharides, segmented polysaccharides,lipopolysaccharides, glycoproteins and proteoglycans. The modifiedproducts or synthetic products may be modified e.g. by oxidation,etherification or esterification, they may further comprise functionalgroups such as aldehyde groups, acetal groups, ketal groups, acylaminogroups, preferably acetylamino groups, anhydro groups or lactone groups.They may further have groups which may be charged, such as —NH₂, —COOH,—OSO₃H, or —OP(O)(OH)₂.

Examples of suitable carbohydrates are known to the skilled artisan andcan be found in conventional textbooks, or monographs. The followinglisting is exemplary only and not meant to restrict the invention:

Suitable sugars are e.g. glucosamin, galaktosamin, neuraminic acid,muraminic acid, sialinic acid, L-fucose, arabinose, xylose, glucuronicacid, gluconic acid or levoglucosan.

Suitable oligosaccarides are e.g. lactose, maltose, cellobiose,chitohexanose, trehalose, isomaltulose, leucrose.

Suitable polysaccharides and derivatives are e.g. hyaluronic acid,deacylated hyaluronic acid, chitosan, chitin 50, fucoidan, carrageenans,dextran, blue dextran, aminated dextran, galaktomannan, glucomannan,pullulan, glycosaminoglycan, heparin, agarose, curdlan, pectin, pecticacid, xanthan, hydroxypropyl cellulose or chitosan, carboxymethylcellulose or chitosan, emulsan, laminaran, inulin, pustulan,scleroglucan, schizophyllan, or mucopolysaccharides.

Further examples of suitable carbohydrates are D-ribose, L-arabinose,D-xylose, L-fucose, D-mannose, D-galactose, D-glucosamine, muramic acid,D-galactosamine; .D-gluocoronic acid, D-mannuronic acid, D-galacturonicacid, L-glycero-D-manno-heptose, neuraminic acid. Further examples ofpolysaccharides are agarose, alginates, carrageenan, cellulosics, suchas acetate, carboxymethyl, ethyl, hydroxyethyl, hydroxypropyl,hydroxypropylmethyl, methyl cellulose, chitin/chitosan, dextran,furcellaran, gellan gum, guar gum, gum arabic, heparin, hyaluronic acid,hydroxypropyl guar, karaya gum, laminaran, locust bean gum, pectin (lowor high methoxyl), rhamsan gum, starches, tragacant gum, welan gum,xanthan gum.

Examples of especially suitable monosaccharides include glycerol,threose, glucose, galactose and fructose. Examples of especiallysuitable oligosaccharides include sucrose, maltose, lactose andcellobiose. Examples of especially suitable polysaccharides includedextrans, starches, dextrins, glycogens, inulin, glycosaminoglycans andmucopolysaccharides, further preferred are dextran, chitosan, hyaluronicacid, mucin, fucoidan, and glucosamin.

Naturally occurring carbohydrates may be modified in order to enhancetheir reactivity with activated surfaces. For example, oxidation ofdextran with periodate yields aldehydes which can react with amines onthe surface of the material; treatment of dextran with bromoacetic acidin alkaline solution places pendant carboxymethyl groups on thepolysaccharide backbone which, in turn, can form ester or amide linkswith surface hydroxyls or amines, respectively; treatment of dextranwith choroethylamine in alkaline solution places pendant aminomethylgroups on the polysaccharide backbone which, in turn, can react withsurface epoxy, acid chloride or tosylate groups.

Step two may be performed by immersing the plasma treated material in asolution or vapour of oligo- or bifunctional compound. For example, thesurface may be immersed in a solution of 0.1-5.0 ml epichlorohydrin(preferably 0.2-2.0 ml), and 10-100 ml of 0.4 ml of 0.4 M sodiumhydroxide (preferably 20-30 ml) in 10-100 ml of diethylene glycoldimethyl ether (preferably 20-30 ml) for 1-6 hours (preferably 4-6hours) at 10-60° C. (preferably 20-30° C.). Alternatively, the surfacemay be immersed in a solution containing 20 ml water, 0.4 ml1,4-butanediol diglycidylether, and 1 ml benzyltrimethylammoniumhydroxide at 60° C. for 5 hours. The sample is then rinsed with water atroom temperature.

The reaction between the carbohydrate and the reactive groups of thesurface is performed in such a way that a highly water retainingcarbohydrate layer is provided on the outermost surface of the novelcomposite material. Preferably the material with an activated surface isplaced in a solution of carbohydrate for an appropriate time. Forexample the method described by S. Lofas and B. Johnsson in J. Chem.Soc.: Chem. Commun. 1526 (1990) may be used. Thus the surface can bereacted with 0.1-15.0 g (preferably 2.0-5.0 g) of dextran (molecularweight 1,000-5,000,000 Da, preferably 500,000-2,000,000 Da) in 10-50 ml(preferably 20-30 ml) of 0.01-5.0 M (preferably 0.1-2.0 M) sodiumhydroxide for 0.1-48 hours (preferably 20-25 hours) at 10-60° C.(preferably 20-30° C.). Excess dextran is washed off by rinsing thesample in distilled water. Alternatively, the material may be immersedin a solution containing 20 ml water, 0.2 g dextran (molecular weight1,000 to 40,000,000 Da (preferably 500,000 to 40,000,000 Da) and 1 mlbenzyltrimethylammonium hydroxide at 60° C. for 18 hours. Again, excessdextran is washed off by rinsing the sample in distilled water.

The invention encompasses all such methods and the biomedical devices,e.g. ophthalmic devices so obtained.

The biomedical devices of the inventions are e.g. implantable biomedicaldevices, such as prostheses, vascular grafts, catheters, pacemakers orshunts, or ophthalmic devices. The ophthalmic device of the invention ise.g. a contact lens, an eye bandage or an intraocular lens, andpreferably it is a contact lens.

In its broadest aspects the invention is directed to a compositematerial, especially a biomedical device, e.g. an ophthalmic device,preferably a contact lens, with one or more, preferably one or two,wettable surfaces capable of holding a continous layer of aqueous fluidthereon which composite material comprises a bulk material and ahydrophilic coating characterized in that the hydrophilic coatingconsists of a carbohydrate, including a modified carbohydrate, attachedcovalently to reactive groups at the surface of the bulk material,either directly or via functional groups of an oligofunctional compound,said oligofunctional compound in turn having functional groups beingcapable of reacting with said reactive groups at the surface of the bulkmaterial and with the carbohydrate, wherein said reactive groups areeither inherently (a priori) present in the bulk material or whereinsaid reactive groups have been attached to the surface of the bulkmaterial by a plasma surface preparation.

A preferred subembodiment of the invention is a biomedical device, e.g.an ophthalmic device wherein reactive groups are inherently present inthe bulk material and wherein the oligofunctional compound is abis-oxirane or an epihalohydrin, preferably a bis-oxirane.

A further preferred subembodiment of the invention is a biomedicaldevice, e.g. an ophthalmic device wherein reactive groups are inherentlypresent in the bulk material, wherein the oligofunctional compound is abis-oxirane and the carbohydrate is a polysaccharide. Said carbohydrateis preferably selected from dextran, chitosan, hyaluronic acid, mucin,fucoidan, and glucosamin.

A further preferred subembodiment of the invention is a biomedicaldevice, e.g. an ophthalmic device wherein reactive groups are inherentlypresent in the bulk material, wherein the oligofunctional compound is adiisocyanate and the carbohydrate is a non-polysaccharide carbohydrate.

A further preferred subembodiment of the invention is a biomedicaldevice, e.g. an ophthalmic device wherein reactive groups are inherentlypresent in the bulk material, wherein the oligofunctional compound is adiisocyanate and the carbohydrate is dextran.

An additionally preferred subembodiment of the invention is a biomedicaldevice, e.g. an ophthalmic device wherein reactive groups are inherentlypresent in the bulk material, and wherein the oligofunctional compoundhas different reactivity with respect to its functional groups. Such anoligofunctional compound may be e.g. a bis-oxirane having differentreactivity with respect to its two functional groups, such as forexample limonene dioxide, vinylcyclohexene dioxide,3,4-epoxycyclohexylmethyl 3,4-epoxy-cyclohexane carboxylate, or it maybe e.g. a diisocyanate having different reactivity with respect to itstwo functional groups, such as for example isophorone diisocyanate,2,4-toluene diisocyanate, or 2,2,4-trimethylhexamethylene diisocyanate.

Another preferred embodiment of the invention is a biomedical device,e.g. an ophthalmic device wherein said reactive groups have beenattached to said surface by a plasma surface preparation and wherein theoligofunctional compound is selected from an epihalohydrin, bis-oxirane,diisocyanate, diacid chloride, and ditosylate.

Within this embodiment it is preferred that the oligofunctional compoundis a bis-oxirane. It is further preferred that the oligofunctionalcompound is a bis-oxirane having different reactivity with respect toits two functional groups.

Another preferred embodiment of the invention is a biomedical device,e.g. an ophthalmic device wherein said reactive groups have beenattached to said surface by a plasma surface preparation and wherein theoligofunctional compound is a bis-oxirane and the carbohydrate is apolysaccharide, which is preferably selected from dextran, chitosan,hyaluronic acid, mucin, fucoidan, and glucosamin.

Another preferred embodiment of the invention is a biomedical device,e.g. an ophthalmic device wherein said reactive groups have beenattached to said surface by a plasma surface preparation and wherein theoligofunctional compound is a diisocyanate. It is further preferred thatthe oligofunctional compound is a diisocyanate having differentreactivity with respect to its two functional groups.

Another preferred embodiment of the invention is a biomedical device,e.g. an ophthalmic device wherein said reactive groups have beenattached to said surface by a plasma surface preparation and wherein theoligofunctional compound is a diisocyanate and the carbohydrate is apolysaccharide, which is preferably selected from dextran, chitosan,hyaluronic acid, mucin, fucoidan, and glucosamin.

A further preferred subembodiment of the invention is a biomedicaldevice, e.g. an ophthalmic device wherein reactive groups are inherentlypresent in the bulk material, wherein the carbohydrate is apolysaccharide which is directly bonded to the reactive groups. Saidcarbohydrate is preferably selected from dextran, chitosan, hyaluronicacid, mucin, fucoidan, and glucosamin.

A further preferred subembodiment of the invention is a biomedicaldevice, e.g. an ophthalmic device wherein reactive groups are inherentlypresent in the bulk material, wherein the carbohydrate is anon-polysaccharide carbohydrate which is directly bonded to the reactivegroups.

A further preferred subembodiment of the invention is a biomedicaldevice, e.g. an ophthalmic device wherein reactive groups are inherentlypresent in the bulk material, wherein the carbohydrate is dextran whichis directly bonded to the reactive groups.

Another preferred embodiment of the invention is a biomedical device,e.g. an ophthalmic device wherein said reactive groups have beenattached to said surface by a plasma surface preparation and wherein thecarbohydrate is a polysaccharide, which is directly bonded to thereactive groups. Said carbohydrate is preferably selected from dextran,chitosan, hyaluronic acid, mucin, fucoidan, and glucosamin.

Another preferred embodiment of the invention is a biomedical device,e.g. an ophthalmic device wherein said reactive groups which have beenattached to said surface by a plasma surface preparation are hydroxy oramino groups and wherein the carbohydrate which is directly bonded tothe reactive groups is preferably selected from dextran, chitosan,hyaluronic acid, mucin, fucoidan, and glucosamin, and is most preferablydextran.

The biomedical devices, e.g. ophthalmic devices according to the presentinvention have a variety of unexpected advances over those of the priorart which make those devices, especially contact lenses, according tothe invention very suitable for practical purposes, e.g. as contactlenses for extended wear. For example, they do have a high surfacewettability which can be demonstrated by their contact angles, theirwater retention and their water-film break up time or tear film break uptime. The water retention time is closely related to the water-filmbreak up time (“BUT”) and the tear film break up time, in that a highwater retention time results in a high water-film break up time or tearfilm break up time.

In addition the biomedical devices, e.g. ophthalmic devices, such ascontact lenses according to this invention have a very pronouncedbiocompatibility combined with good mechanical properties. For example,there are generally no adverse eye effects observed, while theadsorption of proteins or lipids is low, also salt deposit formation islower than with conventional contact lenses. Generally one may statethat there is low fouling, low microbial adhesion and low bioerosionwhile the good mechanical properties can be for example found in a lowfriction coefficient and low abrasion properties.

In summary the ophthalmic devices according to this invention, such ascontact lenses, provide a combination of low spoilation with respect tocell debris, cosmetics, dust or dirt, solvent vapors or chemicals, witha high comfort for the patient wearing such contact lenses in view ofthe soft hydrogel surface which for example provides a very good on-eyemovement of the contact lenses.

The biomedical devices (e.g. renal dialysis membranes, blood storagebags, pacemaker leads or vascular grafts) resist fouling by proteins byvirtue of the continuous layer of bound water, thus reducing the rateand extent of thrombosis. Blood-contacting devices fabricated accordingto the present invention are therefore haemocompatible andbiocompatible.

Further preferred embodiments are apparent to the skilled artisan fromthe disclosure and the examples. However, the examples are illustrativeonly and are not intended to limit the disclosure whatsoever.

Hereinafter two possible reaction schemes are shown whereby epoxy groupsmay be covalently attached onto a plasma treated biomedical device, e.g.a contact lens:

wherein (CL) denotes the surface of a contact lens, (CL)—NH₂ denotes anexemplary amino group present at the surface of said contact lens and(CL)—OH denotes an exemplary hydroxy group present at the surface ofsaid contact lens.

A further reaction scheme shows the covalent attachment of acarbohydrate onto epoxy groups bonded to a biomedical device, e.g. acontact lens:

wherein (CL) denotes the surface of a contact lens, and R₁ and R₂ havethe meaning of a conventional residue extending the chain of acarbohydrate.

Where the carbohydrate contains a trans vicinal diol the carbohydrate,such as e.g. dextran, may be oxidized in part with an appropriateoxidizing agent, e.g. with sodium periodate, in order to obtain ringcleavage and formation of aldehyde functions. Said aldehyde functionsmay be reacted with amino groups, present as reactive groups or asfunctional groups at the surface of the biomedical device, to form an—N═CH-group. Said groups may be reduced with a suitable reducing agentto a hydrolytically stable —NH—CH₂-group linking the carbohydratemolecule to the device surface.

Without limiting the invention, further combinations of chemical groupswhich may be reacted with each other in order to obtain compositematerials according to this invention are e.g. as follows: A carbonylreactive group at the surface of the device is reacted with a hydrazidefunctional group of a dihydrazide while the other hydrazide functionalgroup thereof is reacted with an aldehyde group of a carbohydrate. Analdehyde reactive group at the surface of the device is reacted with anamino group of a carbohydrate, and reduced if desire& An amino reactivegroup or a hydroxy reactive group at the surface of the device isreacted with an epoxide functional group of a diepoxide while the otherepoxide functional group thereof is reacted with an amino or hydroxygroup of a carbohydrate. An amino reactive group or a hydroxy reactivegroup at the surface of the device is reacted with one functional endgroup of an epichlorohydrin while the other functional end group thereofis reacted with an amino or hydroxy group of a carbohydrate. An aminoreactive group or a hydroxy reactive group at the surface of the deviceis reacted with an isocyanato functional group of a diisocyanate whilethe other isocyanato functional group thereof is reacted with an aminoor hydroxy group of a carbohydrate. A carboxy group at the surface ofthe device is reacted with an amino group of a carbohydrate. A reactivegroup at the surface of the device which is replaceable by an amino orhydroxy group is replaced by an amino or hydroxy group of acarbohydrate.

In the examples, if not otherwise indicated, temperatures are given indegrees Celsius, and contact angles are given in degrees.

EXAMPLE 1 (COMPARATIVE)

Commercially available fluoropolymer (Fluorofocon A™) contact lenses areremoved from storage in saline solution, rinsed with distilled water andinserted for in vivo testing (with unpreserved, buffered salinesolution). Each lens is fitted to a subject who is unadapted to contactlens wear. Subjects are chosen to whom the lenses could be adequatelyfitted. The measured variables are: (1) overall wettability, (2) frontsurface break up time (FS BUT), (3) speed of surface drying, (4) surfacecoverage. The variables are assessed immediately after insertion andagain ten minutes after insertion.

EXAMPLE 2 (COMPARATIVE)

Commercially available silicone elastomer (Elastofilcon A™) contactlenses are removed from storage in saline solution, rinsed withdistilled water and then allowed to dry in air prior to measurement ofair/water contact angles.

Contact angles are measured using a modified Kernco-G2 contact anglegoniometer. By placing the sample on a flat stage and placing a drop ofdistilled water on the apex of the anterior lens surface using amicrometer driven syringe, and then aligning rotatable cross hairs inthe eyepiece at a tangent to the curvature of the lens and the drop atthe water/air/lens interface, the sessile contact angle (SCA) can bemeasured. The micrometer driven syringe is then used to graduallyincrease the volume of the drop by injecting more water into it, justuntil the drop begins to advance across the surface, at which point theadvancing contact angle (ACA) is measured using the rotatablecrosshairs. The micrometer driven syringe is then used to graduallydecrease the volume of the drop by withdrawing water from it, until thedrop begins to recede across the surface, at which point the recedingcontact angle (RCA) is measured.

EXAMPLE 3

Commercially available RGP fluoropolymer (Fluorofocon A™) contact lensesare coated with a thin polymer film produced by plasma polymerization ofmethanol vapour at a pressure of 0.7 torr, input power of 10 watts,signal frequency of 300 kHz and treatment time of 1 minute.

The plasma modified contact lenses are reacted with 0.235 ml ofepichlorohydrin in a mixture of 25 ml of 0.4 M NaOH and 25 ml ofdiethylene glycol dimethyl ether at 20° C. for 4 hours. The lenses arethen washed 3 times in distilled water, twice with ethanol and again 3times in distilled water.

Dextran is attached to the epichlorhydrin treated lens surfaces bysoaking in a solution of 3.0 g Dextran dissolved in 25 ml of 0.1 M NaOHfor 20 hours. The lenses are then washed 5 times in distilled water andallowed to dry in air before measuring contact angles. The treatedlenses are then stored in saline solution before testing under identicalconditions as example 1.

The in vitro data in Table 1 reveal a decrease in sessile, advancing andreceding air/water contact angles of the contact lenses when thesurfaces are treated according to this invention.

The in vivo data in Table 2 reveal an increase in wettability by tearfilm when the surfaces are treated according to this invention.

EXAMPLE 4

Example 4 is identical to Example 3, except that the contact lenses arecommercially available silicone elastomer (Elastofilcon A™) contactlenses, and measurements of air/water contact angles are made afterrinsing with distilled water and allowed to dry in air. The results inTable 1 reveal a decrease in sessile, advancing and receding air/watercontact angles of the contact lenses when the surfaces are treatedaccording to this invention.

Brief Description of Tables 1 and 2

Table 1 shows the change in air/water contact angles consequent onattachment of polysaccharide onto the surface of RGP fluoropolymer(Fluorofocon A™) and silicone elastomer (Elastofilcon A™) contactlenses.

Table 2 shows the effect of grafted polysaccharide on the time taken forthe contact lens to dry, for RGP fluoropolymer (Fluorofocon A™) contactlenses.

TABLE 1 Contact Lens SCA* ACA* RCA* Fluorofocon A ™ lenses: Untreatedlenses 111 119 47 Lenses with Dextran (MW = 500,000) 90 95 9 Lenses withDextran (MW = 2'000,000) 80 85 4 Elastofilcon A ™ lenses: Untreatedlenses 102 107 61 Lenses with Dextran (MW = 500,000) 99 104 45 Lenseswith Dextran (MW = 2'000,000) 93 99 17 *SCA, ACA and RCA are thesessile, advancing and receding air/water contact angles respectively.

TABLE 2 Initially After 10 minutes Comparative Comparative VariableExample 3 example 1 Example 3 example 1 Wettability* 3.5 +/− 0.9 2.5 +/−1.3 3.3 +/− 0.6 1.9 +/− 0.7 FS BUT#  10 +/− 3 7 +/− 4 9 +/− 2 5 +/− 2(secs) Speed of 1.4 +/− 0.6 2.1 +/− 0.7 1.3 +/− 0.4 2.9 +/− 0.2 drying⁺Wettability* 0 = surface completely non-wetting 1 = very thin tearlayer, fast break up time (BUT) 2 = moderately thin layer, fast BUT 3 =tear layer slightly thin, BUT approximately equal to interblink interval4 = tear layer thick and smooth, no dry patches, BUT greater thaninterblink interval FS BUT# Front surface break up time Speed of drying⁺1 = slow 2 = moderate 3 = fast

EXAMPLE 5 (COMPARISON)

An important criterion for the usefulness of the present invention isthe time taken for water to recede from 50% of the surface of asubstrate, such as a contact lens. This parameter is abbreviated “WRT”and presented in seconds in this example and hereinafter. The bulkmaterial used is fluorinated ethylene propylene. This material, withoutmodification of its surface has a WRT of <1 second.

EXAMPLE 6

A flat substrate of fluorinated ethylene propylene is subjected to aplasma treatment in the presence of heptylamine. 1 g of polysaccharidein 200 ml water is treated with 3 g NaIO₄ and reacted with the plasmatreated substrate having amino groups at its surface in the presence ofNaCNBH₃ at a pH of 6 to 9. A substrate with a hydrophilic coating isobtained for which the following time taken for water to recede from 50%of the surface (WRT) is measured:

MW WRT polysaccharide (kDa) (sec) a) dextran 9.3 180 b) dextran 74.2 180c) dextran 515 180 d) dextran 2000 180 e) blue dextran 2000 180 f)pectic acid n.d. 180 g) polyquat JR30M n.d. 90

EXAMPLE 7

A flat substrate of fluorinated ethylene propylene is subjected to aplasma treatment in the presence of methanol. The substrate havinghydroxy groups at its surface is treated with 1,4-butanediol diglycidylether in the presence of benzyltrimethylammonium hydroxide and withdextran. A substrate with a hydrophilic coating is obtained for whichthe following time taken for water to recede from 50% of the surface(WRT) is measured:

MW WRT polysaccharide (kDa) (sec) a) dextran 515 75 b) dextran 2000 90c) dextran 2000 210 d) dextran 5-40000 >300

In the following examples 1,4-butanediol diglycidyl ether is replaced bydi(ethyleneglycol)diglycidyl ether (example e), bytetra(ethyleneglycol)diglycidyl ether (example f) or byocta(ethyleneglycol)diglycidyl ether (example g):

e) dextran 2000 150 f) dextran 2000 90 g) dextran 2000 135

EXAMPLE 8

An Elastofilcon contact lens is subjected to a plasma treatment in thepresence of heptylamine. Dextran with a molecular weight (MW) of 74.2kDa is treated with NaIO₄/NaCNBH₃ and reacted with the plasma treatedcontact lens having amino groups at its surface. A contact lens with ahydrophilic coating is obtained for which a time taken for water torecede from 50% of the surface (WRT) of 180 seconds is measured.

EXAMPLE 9

A Tefilcon contact lens is subjected to a plasma treatment in thepresence of heptylamine. Dextran with a molecular weight (MW) of 74.2kDa is treated with NaIO₄/NaCNBH₃ and reacted with the plasma treatedcontact lens having amino groups at its surface. A contact lens with ahydrophilic coating is obtained for which a time taken for water torecede from 50% of the surface (WRT) of 90 seconds is measured. Bycontrast, a Tefilcon contact lens, without modification of its surface,has a WRT of 10 seconds.

EXAMPLE 10

A flat substrate of a) polyurethane, b) glass and c) Al-Kapton issubjected to a plasma treatment in the presence of heptylamine. Apolysaccharide is treated with NaIO₄/NaCNBH₃ and reacted with the plasmatreated substrate having amino groups at its surface. A substrate with ahydrophilic coating is obtained for which the following time taken forwater to recede from 50% of the surface (WRT) is measured:

MW WRT polysaccharide (kDa) (sec) a) dextran 74.2 900 b) dextran 74.2120 c) dextran 74.2 120

EXAMPLE 11

A silicone film, made from UV-cured silicone PS 2067 (Hüls America Inc,Bristol, USA) by casting it on a Folanorm foil (Foex®, Zürich,Switzerland) and irradiation, is placed in an RF-GDP system (radiofrequency glow discharge plasma) and the system is evacuated to 0.1mbar. The film is exposed at a pressure of 0.1 mbar to an oxygen plasmaat a power of about 40 W, at an oxygen flow of 10 nanocubic centimetersfor 30 seconds, thereafter to air with release of the vacuum.

EXAMPLE 12

A polybutadiene film, made from a tetrahydrofuran solution ofpoly(1,2-syndiotactic butadiene)(Polysciences, Inc., cat #16317) bycasting said solution on a Folanorm foil and evaporating thetetrahydrofuran under a nitrogen flow, is modified by the methoddescribed in example 11.

EXAMPLE 13

The plasma treated silicone film of example 11 is placed into adesiccator over about 5 ml of 2,4-tolylene diisocyanate (2,4-TDI). Thedesiccator is heated to 50° C. and evacuated to 0.008 mbar. The reactionwith 2,4-TDI vapors is carried out for 2.5 hours. After cooling to roomtemperature the film is taken off, washed vigorously with dry acetoneand soaked in a DMSO solution (comprising 5% LiCl) of chitosan for 8hours. The modified film is washed thereafter 24 hours with water, driedand analyzed.

EXAMPLE 14 to 16

The following films are treated according to the method of example 13except where specified otherwise:

Example 14: The oxygen plasma treated polybutadiene film of example 12.Time of vapor reaction is 2.5 hours.

Example 15: A poly(hydroxyethyl methacrylate) (p-HEMA) film made from asolution consisting of HEMA (92%), ethylene glycol dimethacrylate (5%)and, as a photoinitiator, Irgacure 184 (3%) by casting it on a Folanormfoil and UV-irradiation. Time of vapor reaction is 6 hours. Time ofreaction with chitosan is only 30 minutes.

Example 16: A polyvinyl alcohol film (PVA) made from a DMSO solution ofPVA 72 000 (Fluka AG) (99%) and isophorone diisocyanate (IPDI),(Aldrich) (1%) by casting it on a Folanorm foil and heating to 70° C.for 2 hours under reduced pressure. Time of vapor reaction is 6 hours.Time of reaction with chitosan is only 30 minutes.

The following table lists the contact angles (“CA”), measured with asystem G 40 (Krüss GmbH, Hamburg Germany), of the polymeric films beforetreatment and after treatment:

CA before CA after Example Material treatment (°) treatment (°) 13silicone 100.4 56.9 14 polybutadiene 79.5 52.5 15 p-HEMA 78.4 67.5 16PVA 47.1 31.5

EXAMPLE 17 to 20

Examples 13 to 16 are repeated with the same 2,4-TDI vapor modifiedfilms, but using, instead of the step of soaking in a chitosan solution,the step of soaking in a 1% solution of hyaluronic acid, comprisingabout 1 mg of catalyst (DBTDL), in DMSO. The hyaluronic acid is obtainedfrom Czechoslovakia (Product ZD Straznice, CSFR).

The following table lists the contact angles (“CA”), measured with asystem G 40 (Krüss GmbH, Hamburg Germany), of the polymeric films beforetreatment and after treatment:

CA before CA after Example Material treatment (°) treatment (°) 17silicone 100.4 57.0 18 polybutadiene 79.5 68.0 19 p-HEMA 77.8 58.3 20PVA 47.1 42.1

EXAMPLE 21 to 24

Polymeric films as described in examples 13 to 16 are soaked in a 5%2,4-TDI solution in a solvent incapable to swell the polymer (forsolvent information see table hereinafter). The reactions are carriedout at room temperature, under nitrogen gas for 12 hours. After reactionthe films are washed in acetone and dried under reduced pressure. Thefilms are thereafter soaked in a 1% DMSO solution (comprising 5% LiCl)of chitosan for 24 hours. The modified films are washed thereafter for24 hours with distilled water, dried and analyzed.

The following table lists the contact angles (“CA”), measured with asystem G 40 (Krüss GmbH, Hamburg Germany), of the polymeric films beforetreatment and after treatment:

Material CA before CA after Example (Solvent) treatment (°) treatment(°) 21 silicone 100.4 59.8 (DMSO) 22 polybutadiene 79.5 58.0 (DMSO) 23p-HEMA 77.8 54.0 (tetrahydrofurane and diethylether) 24 PVA 47.1 37.5(acetonitril)

EXAMPLE 25 to 27

Examples 22 to 24 are repeated with the same 2,4-TDI solution modifiedfilms, but using, instead of the step of soaking in a chitosan solution,the step of soaking in a 1% solution of hyaluronic acid, comprisingabout 1 mg of catalyst (DBTDL), in DMSO.

The following table lists the contact angles (“CA”), measured with asystem G 40 (Krüss GmbH, Hamburg Germany), of the polymeric films beforetreatment and after treatment:

CA before CA after Example Material treatment (°) treatment (°) 25polybutadiene 79.5 59.1 26 p-HEMA 78.0 55.1 27 PVA 48.0 38.0

EXAMPLE 28

Washed and lyophilized SID™ contact lenses (from CIBA Vision, Atlanta,Tefilcon), based on a crosslinked polymer of p-HEMA, are soaked in amixture of 5 ml of tetrahydrofurane, 5 ml of diethylether, 0.2 g ofisophorone diisocyanate (IPDI) and 10 mg of catalyst (DBTDL). Thereaction proceeds at room temperature under nitrogen flow for 12 hours.Thereafter the lenses are washed with acetone, dried and soaked in a0.5% solution of a carbohydrate in DMSO (comprising 5% LiCl) and (exceptfor example 28 d) DBTDL as a catalyst. After 1 to 2 hours the lenses arevigorously washed with water, dried and analyzed.

The following table lists the contact angles (“CA”), measured with asystem G 40 (Krüss GmbH, Hamburg Germany), of the contact lenses aftertreatment (for comparison: the contact angle of an untreated STD contactlens is 77-78°):

Example carbohydrate CA after treatment (°) a) Mucin (Sigma) 53.4 b)Fucoidan 50.5 c) Dextran 26.8 d) Glucosamine (Fluka) 38.9

EXAMPLE 29

Washed and lyophilized EXCELENS™ contact lenses (from CIBA Vision,Atlanta, Adlafilcon), based on a crosslinked polymer of PVA, are soakedin a mixture of 5 ml of tetrahydrofurane, 5 ml of diethylether, 0.2 g ofisophorone diisocyanate (IPDI) and 10 mg of catalyst (DBTDL). Thereaction proceeds at room temperature under nitrogen for 12 hours.Thereafter the lenses are washed with acetone, dried and soaked in a0.5% solution of a carbohydrate in DMSO (comprising 5% LiCl) and (exceptfor example 29 a) DBTDL as a catalys. After 1 to 2 hours the lenses arevigorously washed with water, dried and analyzed.

The following table lists the contact angles (“CA”), measured with asystem G 40 (Krüss GmbH, Hamburg Germany), of the contact lenses aftertreatment (for comparison: the contact angle of an untreated EXCELENScontact lens is 69-70°):

Example carbohydrate CA after treatment (°) a) Chitosan 63.1 b) Fucoidan(Sigma) 61.3 c) Dextran (Fluka) 44.9

EXAMPLE 30

A flat substrate of fluorinated ethylene propylene (FEP) orperfluoropolyether (PFPE) is subjected to a plasma treatment in thepresence of a) ammonia, b) ethylene diamine or c) heptylamine. Dextranof 74.2 kDa molecular weight is treated with NaIO₄/NaCNBH₃ and reactedwith the plasma treated substrate having amino groups at its surface. Asubstrate with a hydrophilic coating is obtained for which the followingtime taken for water to recede from 50% of the surface (WRT) ismeasured:

substrate plasma gas WRT (sec) a) FEP ammonia 160 b) FEP ethylene 160diamine c) PFPE heptylamine 110

EXAMPLE 31

Different contact lenses are subjected to a plasma treatment in thepresence of ammonia or heptylamine. Dextran of 74.2 kDa molecular weightis treated with NaIO₄/NaCNBH₃ and reacted with the plasma treatedcontact lenses having amino groups at their surface. Contact lenses witha hydrophilic coating are obtained for which the following time takenfor water to recede from 50% of the surface (WRT) is measured:

contact lens material plasma gas WRT (sec) a) Tefilcon ammonia 60 b)silicone material* ammonia 115 c) silicone material* heptylamine 100 d)Atlafilcon A heptylamine 130 *The silicone material used here is acopolymer comprising 15 weight percent methyl methacrylate, 15 weightpercent tris(trimethylsilyloxy)silyl-propyl methacrylate and 70 weightpercent of a macromer having units of hydroxybutyl-terminateddimethylsiloxane, and of isophorone diisocyanate the isocyanate groupsof which have been reacted with the terminal hydroxy groups of thesiloxane, which macromer is terminated with # isocyanatoethylmethacrylate, the isocyanato groups of which have been reacted with aterminal hydroxy group of the siloxane.

What is claimed is:
 1. A composite materials having at least onewettable surface capable of holding a continuous layer of aqueous fluidtherein, which material comprises: (a) a bulk base material, and (b) ahydrophilic coating, wherein the hydrophilic coating consists of acarbohydrate directly and covalently attached to amino groups at thesurface of the bulk base material, wherein said amino groups are eitherinherently (a priori) present in the base material or have been attachedto the surface of the bulk base material by plasma surface treatment. 2.A composite material according to claim 1 wherein the amino groups areinherently present in the base material.
 3. A composite materialaccording to claim 1 which is a biomedical device.
 4. A compositematerial according to claim 1 which is an ophthalmic device.
 5. Acomposite material according to claim 1 which is a contact lens.
 6. Acomposite material according to claim 1 wherein the carbohydrate isselected from dextran, chitosan, hyaluronic acid, mucin, fucoidan, andglucosamine.
 7. A composite material according to claim 1 wherein saidamino groups have been directly and covalently attached to said surfaceby plasma surface treatment.
 8. A composite material according to claim1 wherein said amino groups have been directly and covalently attachedto said surface by plasma surface treatment and the carbohydrate is apolysaccharide.
 9. A composite material according to claim 8 wherin thecarbohydrate is selected from dextran, chitosan, hyaluronic acid, mucin,fucoidan, and glucosamine.
 10. A composite material according to claim 1wherein amino groups are inherently present in the base material whereinthe carbohydrate is a polysaccharide.
 11. A composite material accordingto claim 10 wherin the carbohydrate is selected from dextran, chitosan,hyaluronic acid, mucin, fucoidan, and glucosamine.
 12. A compositematerial according to claim 1 wherein amino groups are inherentlypresent in the base material, wherein the carbohydrate is anon-polysaccharide carbohydrate with is directly attached to the aminogroups.
 13. A composite material according to claim 1 wherein aminogroups are inherently present in the base material, wherein thecarbohydrate is dextran.
 14. A process for the manufacture of a wettablecomposite material with one or more wettable surface capable of holdinga continuous layer of aqueous fluid thereon, wherein said compositematerial includes a bulk base material and a hydrophilic coating of acarbohydrate directly attached covalently to amino groups at the surfaceof the base materials, said process comprising the steps of: (1)covalently attaching amino groups onto the surface of a preformed basematerial by subjecting the preformed base material to a gas plasmaestablished in a vapor containing at least one amine compound; (2)optionally treating the carbohydrate with a reagent which modifies saidcarbohydrate such that said carbohydrate is capable of reacting with theamino groups; (3) reacting said amino groups on the surface with thecarbohydrate to immobilize the carbohydrate onto the surface; and (4)optionally treating the surface-immobilized carbohydrate with a reagentto stabilize the bond between the carbohydrate and the surface.
 15. Acomposite material according to claim 1, wherein the amino groups arecovalently attached to the surface of preformed base material bysubjecting the preformed base material to a low pressure plasma in avapor of an alkylamine having up to eight carbon atoms under conditionswhereby amino groups are formed on the desired surface of the basematerial.
 16. A composite material according to claim 15 wherein thealkyl amine is heptylamine.
 17. A composite material according to claim15 wherein the alkyl amine is ethylamine.
 18. A composite materialaccording to claim 15 wherein the alkyl amine is methylamine.
 19. Aprocess of claim 14 wherein the amine is an alkyl amine having up toeight carbon atoms.
 20. A process of claim 14 wherein the alkyl amine isheptylamine.
 21. A process of claim 14 wherein the alkyl amine isethylamine.
 22. A process of claim 14 wherein the alkyl amine ismethylamine.